JP6498299B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus including an injection pipe.

  In the conventional refrigeration cycle apparatus, when the high pressure of the refrigerant circuit becomes equal to or higher than the set pressure, a high pressure switch that stops protection of the compressor, a high pressure sensor that detects the high pressure of the refrigerant circuit or its pressure saturation temperature, High pressure control means for performing high pressure protection control. And the high pressure control means which calculates | requires the average of the detection pressure of the multiple times in a high pressure sensor, and performs high pressure protection control when the average value exceeds a threshold value is proposed (for example, refer patent document 1). .

JP 2011-252621 A

  In the refrigeration cycle apparatus in which the heat medium (for example, water) flowing through the heat medium flow path and the refrigerant flowing through the condenser of the refrigerant circuit exchange heat, the refrigerant circuit is set so that the temperature of the heat medium becomes an arbitrary set temperature The condensing temperature is controlled. However, when the set temperature of the heat medium is high, there is a problem that the pressure (high pressure) of the refrigerant discharged from the compressor of the refrigerant circuit increases as the condensation temperature increases.

  The technique described in Patent Document 1 calculates an average of a plurality of detected pressures by a high-pressure sensor in order to suppress frequent stoppage in high-pressure protection, and high-pressure protection control works when the average value exceeds a threshold value. I am doing so. However, since the high pressure protection is entered when the average pressure reaches a predetermined value, high pressure suppression is not fundamentally achieved.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a refrigeration cycle apparatus that can suppress an increase in high-pressure pressure of a refrigerant circuit.

The refrigeration cycle apparatus according to the present invention includes a compressor, a condenser, a first expansion valve, and an evaporator, and includes a refrigerant circuit that circulates refrigerant and a control device that controls the compressor, and the compressor Has a compression chamber and an injection port for injecting refrigerant into the compression chamber, and the refrigerant circuit includes an internal heat exchanger provided between the condenser and the first expansion valve. An injection pipe for connecting a branch portion provided between the internal heat exchanger and the first expansion valve and the injection port via the internal heat exchanger, and the branch of the injection pipe And a second expansion valve provided between the internal heat exchanger, and the internal heat exchanger includes a first refrigerant that is a refrigerant flowing out of the condenser, and the injection Divert to pipe A second refrigerant is a refrigerant whose serial expanded by the second expansion valve, which performs the heat exchange, the refrigerant is injected into the compression chamber from the injection port is a two-phase refrigerant, the condenser, Heat exchange is performed between the refrigerant flowing through the refrigerant circuit and the heat medium passing through the condenser, and the control device determines the drive frequency of the compressor based on the temperature of the heat medium flowing out from the condenser. The amount of the refrigerant to be controlled and enclosed in the refrigerant circuit is an amount of the first refrigerant flowing out of the condenser in a two-phase state in a state where the driving frequency is controlled.

  According to the present invention, the heat transfer coefficient in the condenser can be improved by making the refrigerant flowing out of the condenser into a two-phase state. Therefore, even when the temperature of the refrigerant flowing into the condenser rises, an increase in the high pressure of the refrigerant circuit can be suppressed.

It is a circuit block diagram which shows the structure of the refrigerating-cycle apparatus which concerns on Embodiment 1 of this invention. It is a ph diagram which shows the state of the refrigerant | coolant in the refrigerant circuit used as the premise of Embodiment 1 of this invention. It is a ph diagram which shows the state of the refrigerant in refrigerant circuit 30 concerning Embodiment 1 of the present invention. It is a figure which shows typically the structure of the compressor 1 which concerns on Embodiment 2 of this invention.

  Embodiments of a refrigeration cycle apparatus according to the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below. In the following description, the temperature and pressure levels are not particularly determined in relation to absolute values, but are relatively determined in the operation of the refrigeration cycle apparatus.

Embodiment 1 FIG.
A refrigeration cycle apparatus according to Embodiment 1 of the present invention will be described. FIG. 1 is a circuit configuration diagram showing the configuration of the refrigeration cycle apparatus according to the present embodiment. The refrigeration cycle apparatus supplies hot or cold heat to a fluid (for example, a liquid heat medium or air such as water, antifreeze, or brine) that is a heat transfer medium (heat medium) in air conditioning or the like. In this Embodiment, the refrigerating cycle apparatus which supplies warm heat to water is illustrated.

  As shown in FIG. 1, the refrigeration cycle apparatus in the present embodiment has a refrigerant circuit 30 for circulating the refrigerant. The refrigerant circuit 30 has a main circuit in which the compressor 1, the condenser 2, the first expansion valve 4 and the evaporator 5 are sequentially connected in an annular manner through a refrigerant pipe.

  The compressor 1 compresses the sucked low-pressure refrigerant and discharges it as a high-pressure refrigerant. As the compressor 1, various compressors, such as a scroll compressor, can be used, for example. The compressor 1 includes a compression unit that includes a compression chamber that compresses a refrigerant, a motor that drives the compression unit, and a shell that houses the compression unit and the motor. Refrigerating machine oil that lubricates the sliding portion in the compressor 1 is stored at the bottom of the shell. For example, the compressor 1 can arbitrarily change the drive frequency based on a command signal sent from the control device 100 described later. The compression port of the compressor 1 is provided with an injection port 1a. The injection port 1a is for injecting a medium-pressure gas-liquid two-phase refrigerant into a medium-pressure compression chamber in the middle of the compression stroke in the compression section. Here, the medium pressure is lower than the high pressure in the refrigerant circuit 30 (for example, the discharge pressure of the compressor 1 or the pressure in the condenser 2), and the low pressure (for example, the suction pressure of the compressor 1 or the evaporator). Pressure within 5).

  The condenser 2 is a load-side heat exchanger that performs heat exchange between the high-pressure refrigerant compressed by the compressor 1 and water (an example of a heat medium) that flows through a water flow path 20 described later. The condenser 2 is, for example, a plate heat exchanger in which a plurality of heat transfer plates are stacked.

  The first expansion valve 4 is a valve that expands the refrigerant by decompressing it. The first expansion valve 4 is, for example, an electronic expansion valve that can adjust the opening degree based on a command signal from the control device 100. The evaporator 5 is a heat exchanger on the heat source side that performs heat exchange between the refrigerant decompressed by the first expansion valve 4 and an external fluid (for example, outdoor air) to evaporate the refrigerant to be in a gas phase state.

  The refrigerant circuit 30 further includes an internal heat exchanger 3, an injection pipe 7, and a second expansion valve 6. The internal heat exchanger 3 is provided between the condenser 2 and the first expansion valve 4 in the main circuit.

  The injection pipe 7 is a refrigerant pipe that connects the branch portion 18 provided between the internal heat exchanger 3 and the first expansion valve 4 in the main circuit and the injection port 1a of the compressor 1. The injection pipe 7 divides a part of the refrigerant flowing between the internal heat exchanger 3 of the main circuit and the first expansion valve 4 and injects it into the compression chamber of medium pressure of the compressor 1 through the injection port 1a. Is.

  The second expansion valve 6 is provided between the branch portion 18 and the internal heat exchanger 3 in the injection pipe 7. The second expansion valve 6 expands the high-pressure refrigerant divided into the injection piping 7 by reducing the pressure to a medium pressure. The second expansion valve 6 is an electronic expansion valve capable of adjusting the opening degree based on a command signal from the control device 100, for example.

  The internal heat exchanger 3 includes a high-pressure refrigerant (for example, a two-phase refrigerant) that has flowed out of the condenser 2 in the main circuit, and a medium-pressure two-phase refrigerant that is diverted to the injection pipe 7 and decompressed by the second expansion valve 6. And a heat exchanger that performs heat exchange.

  The water channel 20 is constituted by piping or the like, and becomes a channel through which water flows. For example, water may be circulated by connecting the pipe of the water channel 20 in a ring shape. The water flow path 20 is provided with a pump 8 that delivers water.

  The control device 100 is configured by a microcomputer, for example, and includes a CPU, a RAM, a ROM, and the like. A control program and the like are stored in the ROM. Detection values are input to the control device 100 from various sensors that detect the pressure and temperature of the refrigerant in the refrigerant circuit 30 and the temperature of water in the water flow path 20. The control device 100 controls each component of the refrigeration cycle apparatus based on the detection value from each sensor.

<Control action>
Next, the control operation of the control device 100 will be described.
The control device 100 controls the drive frequency of the compressor 1 so that the temperature of the water flowing out of the condenser 2 becomes a set temperature. Here, the set temperature is a temperature arbitrarily set in advance by a user or the like. For example, the control device 100 acquires a detection value from a temperature sensor that detects the temperature of water flowing out of the condenser 2. When the water temperature is lower than the set temperature, the control device 100 increases the drive frequency of the compressor 1 and increases the circulation amount of the refrigerant. On the other hand, when the temperature of water is higher than the set temperature, the control device 100 decreases the drive frequency of the compressor 1 and decreases the circulation amount of the refrigerant.

  Further, the control device 100 controls the opening degree of the first expansion valve 4 so that the subcool of the refrigerant flowing out of the condenser 2 becomes a predetermined value (including 0K). Further, the control device 100 controls the opening degree of the second expansion valve 6 so that the subcool of the refrigerant flowing into the first expansion valve 4 becomes a predetermined value.

<Refrigerant amount>
The amount of refrigerant sealed in the refrigerant circuit 30 is such that the refrigerant flowing out of the condenser 2 in a state where the driving frequency of the compressor 1 is controlled so that the temperature of the water flowing out of the condenser 2 becomes a set temperature. It is the amount that results in a gas-liquid two-phase state.

<Operation of refrigerant>
First, as a premise of the present embodiment, the operation of the refrigeration cycle apparatus in which the refrigerant circuit 30 is filled with an amount of refrigerant that makes the refrigerant flowing out of the condenser 2 into a liquid single phase will be described. FIG. 2 is a ph diagram showing the state of the refrigerant in the refrigerant circuit that is the premise of the present embodiment. The horizontal axis of FIG. 2 represents enthalpy [kJ / kg], and the vertical axis represents pressure [MPa].

  The high-temperature and high-pressure gas refrigerant (point a1 in FIG. 2) discharged from the compressor 1 flows into the condenser 2. The gas refrigerant that has flowed into the condenser 2 is cooled and condensed by heat exchange with water flowing through the water flow path 20, and becomes a supercooled liquid refrigerant (point b1). On the other hand, the water in the water flow path 20 is heated by the heat radiated from the refrigerant (mainly the latent heat of condensation of the refrigerant) to become hot water. The liquid refrigerant that has flowed out of the condenser 2 is further subcooled by heat exchange in the internal heat exchanger 3 (point c1). The liquid refrigerant flowing out of the internal heat exchanger 3 is decompressed by the first expansion valve 4 and becomes a low-pressure two-phase refrigerant (point d1). The two-phase refrigerant that has flowed out of the first expansion valve 4 flows into the evaporator 5. The two-phase refrigerant that has flowed into the evaporator 5 is heated and evaporated by heat exchange with the external fluid, and becomes a low-pressure gas refrigerant (point e1). The low-pressure gas refrigerant that has flowed out of the evaporator 5 is sucked into the compressor 1.

  A part of the liquid refrigerant flowing out from the internal heat exchanger 3 is divided into the injection pipe 7. The liquid refrigerant branched into the injection pipe 7 is depressurized by the second expansion valve 6 and becomes a medium-pressure two-phase refrigerant having a low dryness (point h1). This two-phase refrigerant is heated by heat exchange in the internal heat exchanger 3, and becomes a medium-pressure two-phase refrigerant having a high dryness (point i1). The medium-pressure two-phase refrigerant that has flowed out of the internal heat exchanger 3 is injected into a compression chamber that is in the middle of the compression stroke (for example, a pressure approximately halfway between the suction pressure and the discharge pressure) via the injection port 1a. .

  The low-pressure gas refrigerant sucked into the compressor 1 joins the medium-pressure two-phase refrigerant injected through the injection port 1a (point g1) when it is compressed to the medium pressure in the compression chamber (point f1). ). The merged refrigerant is further compressed in the compression chamber and discharged as a high-temperature and high-pressure gas refrigerant (point a1).

  Next, the operation of the refrigeration cycle apparatus according to the present embodiment will be described. The refrigerant circuit 30 according to the present embodiment is filled with an amount of refrigerant such that the refrigerant flowing out of the condenser 2 becomes a gas-liquid two-phase. FIG. 3 shows the refrigerant circuit 30 according to the present embodiment. It is a ph diagram which shows the state of the refrigerant | coolant in. The horizontal axis of FIG. 3 represents enthalpy [kJ / kg], and the vertical axis represents pressure [MPa].

  As shown in FIG. 3, the basic state of the refrigerant in the present embodiment is the same as the ph diagram shown in FIG. The points a2, c2, d2, e2, f2, g2, h2, and i2 in FIG. 3 correspond to the points a1, c1, d1, e1, f1, g1, h1, and i1 in FIG. 2, respectively. However, the state of the refrigerant flowing out of the condenser 2 is a liquid phase (point b1) in FIG. 2, but is a gas-liquid two phase (point b2) in FIG. On the other hand, the refrigerant flowing into the first expansion valve 4 is in a liquid phase in both FIGS. 2 and 3 (points c1 and c2). For this reason, in the present embodiment, the difference between the enthalpy of the refrigerant flowing out from the condenser 2 and the enthalpy of the refrigerant flowing into the first expansion valve 4 becomes large. Therefore, in this embodiment, it is necessary to increase the amount of heat exchange in the internal heat exchanger 3. In the configuration of the present embodiment, in order to increase the heat exchange amount in the internal heat exchanger 3, it is necessary to increase the amount of refrigerant that is diverted to the injection pipe 7.

  However, when the amount of refrigerant that flows into the injection pipe 7 is increased, the amount of liquid refrigerant that flows into the compressor 1 increases. For this reason, when the injection position of the liquid refrigerant is not appropriate, the liquid refrigerant flowing into the compressor 1 may be mixed with the refrigerating machine oil at the bottom of the shell, and the refrigerating machine oil may be diluted to lower the concentration. When the refrigeration oil is diluted, problems such as seizure of the compressor 1 are likely to occur due to poor lubrication of the sliding portion.

  In this regard, in the present embodiment, the medium pressure refrigerant that has been depressurized by being diverted to the injection pipe 7 is injected into the medium pressure compression chamber in the middle of the compression stroke via the injection port 1a without passing through the shell bottom. The For this reason, even if the amount of liquid refrigerant injected into the compression chamber of medium pressure increases, the refrigerating machine oil at the bottom of the shell is hardly diluted. Thereby, even when the amount of refrigerant branched into the injection pipe 7 is increased, problems such as seizure of the compressor 1 can be prevented, and the reliability of the compressor 1 can be improved. Therefore, the heat exchange amount of the internal heat exchanger 3 can be increased while ensuring the reliability of the compressor 1.

  Moreover, in this Embodiment, since a refrigerant | coolant becomes a two-phase state also in the exit of the condenser 2, the heat transfer rate in the condenser 2 can be improved. Therefore, even when the temperature of the refrigerant flowing into the condenser 2 rises, an increase in the high pressure of the refrigerant circuit 30 can be suppressed. Thereby, the operating range of the refrigeration cycle apparatus can be expanded.

  Furthermore, in the present embodiment, since the liquid single-phase refrigerant can flow into the first expansion valve 4, the flow resistance of the refrigerant generated in the first expansion valve 4 can be reduced. Thereby, since it is not necessary to enlarge the 1st expansion valve 4, the 1st expansion valve 4 can be reduced in size. In addition, noise generated in the first expansion valve 4 can be reduced, and durability and reliability of the first expansion valve 4 can be improved.

Embodiment 2. FIG.
A refrigeration cycle apparatus according to Embodiment 2 of the present invention will be described. The refrigeration cycle apparatus according to the present embodiment is characterized in that the compressor 1 is a low-pressure shell type. The overall configuration of the refrigerant circuit 30 is the same as that of the first embodiment.

  FIG. 4 is a diagram schematically showing the configuration of the compressor 1 according to the present embodiment. As shown in FIG. 4, the compressor 1 includes a compression unit 10 including a compression chamber that compresses a refrigerant, a motor 12 that drives the compression unit 10, and a shell 9 that houses the compression unit 10 and the motor 12. Have. The motor 12 and the compression unit 10 are connected by a shaft 11 that transmits the driving force of the motor 12 to the compression unit 10. An oil sump 17 for storing refrigeration oil is provided at the bottom of the shell 9. Connected to the shell 9 is a suction pipe 13 for sucking low-pressure gas refrigerant flowing out from the outlet of the evaporator 5. Since the compressor 1 is a low-pressure shell type, the low-pressure gas refrigerant sucked from the suction pipe 13 is sucked into the compression unit 10 via the suction space in the shell 9.

  The compression unit 10 is provided with a suction port 16 and an injection port 1a. The suction port 16 sucks the gas refrigerant in the suction space in the shell 9 into the compression chamber of the compression unit 10. The injection port 1a is for injecting a medium-pressure gas-liquid two-phase refrigerant into a medium-pressure compression chamber in the middle of the compression stroke. An injection pipe 7 is connected to the injection port 1a. In addition, a discharge pipe 15 that discharges the high-pressure gas refrigerant compressed by the compression unit 10 to the inlet side of the condenser 2 is connected to the compression unit 10.

  In particular, in the low-pressure shell type compressor 1, when the injection position of the liquid refrigerant is not appropriate, the liquid refrigerant flowing into the compressor 1 may be mixed with the refrigerating machine oil at the bottom of the shell 9, and the refrigerating machine oil may be diluted. is there. In the present embodiment, the medium-pressure refrigerant that has been depressurized by being diverted to the injection pipe 7 is injected into the medium-pressure compression chamber through the injection pipe 7 and the injection port 1a without passing through the suction space in the shell 9. The For this reason, even if the amount of liquid refrigerant injected into the compression chamber of medium pressure increases, the refrigerating machine oil at the bottom of the shell 9 is difficult to be diluted. As a result, even when the amount of refrigerant diverted to the injection pipe 7 is increased, problems such as seizure of the compressor 1 can be prevented more reliably, and the reliability of the compressor 1 can be improved.

  As described above, the refrigeration cycle apparatus according to the above embodiment includes the compressor 1, the condenser 2, the first expansion valve 4, and the evaporator 5, the refrigerant circuit 30 that circulates the refrigerant, and the compressor 1. The compressor 1 has a compression chamber and an injection port 1a for injecting a refrigerant into the compression chamber, and the refrigerant circuit 30 includes the condenser 2 and the first expansion. The internal heat exchanger 3 provided between the valve 4, the branch portion 18 provided between the internal heat exchanger 3 and the first expansion valve 4, and the injection port 1 a are connected to the internal heat exchanger 3. The injection pipe 7 connected via the second expansion valve 6 provided between the branch portion 18 and the internal heat exchanger 3 of the injection pipe 7, and the internal heat exchanger 3. Is a first refrigerant which is a refrigerant flowing out of the condenser 2; Heat exchange with the second refrigerant, which is a refrigerant diverted to the injection pipe 7 and expanded by the second expansion valve 6, and the condenser 2 passes through the condenser 2 and the refrigerant flowing through the refrigerant circuit 30. The controller 100 controls the driving frequency of the compressor 1 based on the temperature of the water flowing out of the condenser 2 and is enclosed in the refrigerant circuit 30. The amount of the refrigerant is an amount by which the first refrigerant becomes a two-phase state in a state where the drive frequency of the compressor 1 is controlled by the control device 100.

  According to this configuration, since the refrigerant flowing out of the condenser 2 is in a two-phase state, the heat transfer coefficient in the condenser 2 can be improved. Therefore, even when the temperature of the refrigerant flowing into the condenser 2 rises, an increase in the high pressure of the refrigerant circuit 30 can be suppressed.

  In the refrigeration cycle apparatus according to the above embodiment, the compressor 1 may be a low-pressure shell type. According to this configuration, even if the amount of liquid refrigerant injected into the medium pressure compression chamber increases, the refrigerating machine oil at the bottom of the shell 9 is difficult to be diluted. As a result, even when the amount of refrigerant diverted to the injection pipe 7 is increased, problems such as seizure of the compressor 1 can be more reliably prevented.

  The above embodiments can be implemented in combination with each other.

  DESCRIPTION OF SYMBOLS 1 Compressor, 1a Injection port, 2 Condenser, 3 Internal heat exchanger, 4 1st expansion valve, 5 Evaporator, 6 2nd expansion valve, 7 Injection piping, 8 Pump, 9 Shell, 10 Compression part, 11 axis , 12 Motor, 13 Suction piping, 15 Discharge piping, 16 Suction port, 17 Oil sump, 18 Branch, 20 Water flow path, 30 Refrigerant circuit, 100 Control device.

Claims (2)

A refrigerant circuit having a compressor, a condenser, a first expansion valve and an evaporator, and circulating the refrigerant;
A control device for controlling the compressor;
With
The compressor has a compression chamber, and an injection port for injecting a refrigerant into the compression chamber,
The refrigerant circuit is
An internal heat exchanger provided between the condenser and the first expansion valve;
An injection pipe for connecting the branch portion provided between the internal heat exchanger and the first expansion valve and the injection port via the internal heat exchanger;
A second expansion valve provided between the branch portion and the internal heat exchanger in the injection pipe;
In addition,
The internal heat exchanger performs heat exchange between a first refrigerant that is a refrigerant that has flowed out of the condenser and a second refrigerant that is a refrigerant that is diverted to the injection pipe and expanded by the second expansion valve. And
The refrigerant injected into the compression chamber from the injection port is a two-phase refrigerant,
The condenser performs heat exchange between a refrigerant flowing through the refrigerant circuit and a heat medium passing through the condenser,
The control device controls the drive frequency of the compressor based on the temperature of the heat medium flowing out of the condenser,
The refrigeration cycle apparatus, wherein the amount of refrigerant sealed in the refrigerant circuit is an amount of the first refrigerant flowing out of the condenser in a two-phase state when the driving frequency is controlled.   The refrigeration cycle apparatus according to claim 1, wherein the compressor is a low-pressure shell type.

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